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Full text of "Metallurgy Of Cast Iron"

CHAPTER LI.
RESULTS OF VARIATION IN THE FLUIDITY   OF   METAL   AFFECTING PHYSICAL TESTS.
Variation in the fluidity of molten metal is "a factor which, the author has discovered to be very important to note in considering the depth of an iron's chill, taken by means of a test bar or " chill block." It is a point which does away with past records or statistics which have been compiled by some from deductions taken from the depth of a chill, by the pronounced manner in which it asserts itself in giving evidence of being affected by the degree of fluidity at which a test bar is poured. In experiments with iron poured " hot " and " dull," the author has made the thickness of chill as great again in one case as in the other. Take, for instance, two test bars and pour one hot so that the iron will run up in the fluidity strips described in Chapter LXVL, page 509, about six inches high, and then cool the iron so as it will only run. tip about an inch: it will be found upon breaking the bars to test the chill that the hot-poured bar will have chilled about as much again as the dull-poured otic. I have not accepted this principle as a fact from a test or two, but have made many to fully assure myself that the principle is correct.a skimmer or rod, will act as if it were covered with an oxide or scum. While hot, it will often boil in the ladle .as if bubbles of gas were escaping from below. It also emits many sparks, which is the chief characteristic phenomenon of hard iron and cannot be better explained than in the language of Tomlinson, who says: